In general, a hair style is an important factor in the cosmetic treatment of a woman, and is set variously depending on dresses, times and places.
As a method of setting the hair style, a method of making waves in the hair is widely used. For this purpose, permanent rods were devised and are used.
FIG. 9 is an exploded perspective view of a permanent rod of the related art.
As shown in FIG. 9, the permanent rod of the related art includes a tubular rod body part 111 having a circular cross-section and an auxiliary rod member 120 which engages with the rod body part 111.
The rod body part 111 has a member fitting recess 111b having an arc-shaped cross-section that is greater than 180°. The member fitting recess 111b extends along the length of the rod body part 111.
The auxiliary rod member 120 has the shape of a hollow cylinder.
The rod body part 111 and the auxiliary rod member 120 respectively have injection-holes 111a and 120a. 
With reference to FIG. 10, a description will be given below of a method of making waves in the hair using the permanent rod of the related art having this configuration.
First, the distal portion of the hair is wound around the auxiliary rod member 120.
Afterwards, the auxiliary rod member 120 with the hair wound thereon is forcibly fitted into the member fitting recess 111b. 
After that, a length of the remaining portion of the hair that is desired to be waved is wound on the rod body part 111.
Afterwards, a neutralizer is injected through the injection-holes 111a and 120a when about 30 to 40 minutes have elapsed after the hair was wound on the rod body part 111.
After that, when about 10 to 20 minutes have elapsed after the neutralizer was injected, the hair is unwound from the rod body part 111 and the auxiliary rod member 120.
Finally, the hair unwound from the rod body part 111 and the auxiliary rod member 120 is washed.
The related-art permanent rod having the above-mentioned configuration was disclosed in Korean Utility Model Application No. 20-1993-0001104 (titled “ROLL TO BE USED STRAIGHT PERMANENT WAVE”).
However, according to the permanent rod of the related art, the rod body part 111 does not have any structure that can make any other waves except for the method of winding the hair thereon. It was impossible to make various waves, which is problematic.